They severely restricted the buying of SIM cards after the Mumbai terror attacks on the flimsy basis that the terrorists used cell phones to coordinate them .

In practice it means that it's a massive pain to get a local number when visiting family.

VOIP intra-country is also illegal, but it's not clear if that's regulatory capture or for similar "national security" grounds.

China is already there, leading the pack.

If you are Uighur ethnicity you need to use a special government issued “phone” or force installed app. They really use it as a tracking device.

https://www.hrw.org/news/2019/05/01/interview-chinas-big-bro...

Satellite phones are banned.